More and more consumer and industrial equipment includes a variable speed transmission mechanism as the operative connection between the engine and the drive wheels of a vehicle or tractor. Typical examples include hydrostatic transmission garden tractors and continuously variable belt transmission lawn and garden tractors. These types of variable speed transmissions give the manufacturer of the equipment a fairly reliable transmission for the device while providing the user of such equipment with an intuitively operated vehicle speed and direction control mechanism. However, one major limitation to these variable speed devices is the difficulty in accurately and reliably locating the transmission in a neutral position (such as would occur when the vehicle is being stopped). This causes a creep of the vehicle (if no brake is applied) or an unnecessary engine load (if a brake is applied). The creep normally necessitates the use of a separate braking mechanism in order to retain the vehicle or tractor in a single position even though the transmission control might be in a nominal neutral position. The unnecessary engine load increases the amount of wear on both the engine and the transmission: the transmission, being constantly engaged, uses at least some of the engine power as heat, wheel rotation or other waste product. The lack of neutral in addition complicates the life of the operator by forcing the operator to utilize some separate mechanism (a bypass value, a clutch, etc.) in order to insure an effective neutral for the vehicle. Some conventional cures for the lack of positive neutral (such as a fluidic neutral bypass dump value in a hydrostatic transmission) present problems in the ongoing operation of the vehicle (such as loss of control on hills for a fluidic neutral bypass--the back pressure of the transmission being needed to keep the vehicle in position). These difficulties and others present significant obstacles for the utilization of variable speed transmissions.
This present invention is directed towards providing a simple control mechanism for placing the variable speed transmission in a neutral or otherwise known condition.